August 12th, 2011
Econintersect: When deep ocean hydrothermal vents (pictured right) were first discovered more than 30 years ago, researchers were astounded to find that they were inhabited by lush communities of animals such as worms, mollusks and crustaceans, most of which were completely unknown to science. Just how these life forms operated so far from any source of light which sustains the photosynthesis processes used by much of terrestial life was a mystery intially.
Follow up:In the past 30 years research has determined that, rather than photosynthesis, these life forms where maintained by processes that have been named "chemosynthesis." From R&D Magazine Online News:
Deep-sea hydrothermal vents are formed at mid-ocean spreading centers where tectonic plates drift apart and new oceanic crust is created by magma rising from deep within the Earth. When seawater interacts with hot rock and rising magma, it becomes superheated, dissolving minerals out of the Earth’s crust. At hydrothermal vents, this superheated energy-laden seawater gushes back out into the ocean at temperatures of up to 400 degrees Celsius, forming black smoker chimneys where it comes into contact with cold deep-sea water. These hot fluids deliver inorganic compounds such as hydrogen sulfide, ammonium, methane, iron and hydrogen to the oceans.
The organisms living at hydrothermal vents oxidize these inorganic compounds to gain the energy needed to create organic matter from carbon dioxide. Unlike on land, where sunlight provides the energy for photosynthesis, in the dark depths of the sea, inorganic chemicals provide energy for life in a process called chemosynthesis.
Before now there have been two types of chemosynthesis found in the deep marine communities, involving oxidation of hydrogen sulfide and of methane. An article in Nature this week describes a third process that involves the oxidation of hydrogen as the energy source for life. This oxidation process is the same that takes place in hydrogen fuel cells that are being researched as an alternative energy production process for electricity and automobile propulsion.
Researchers from Bremen and Kiel used deep diving submersibles to study marine life at depths of nearly two miles. They found that a deep-sea mussel, Bathymodiolus puteoserpentis, which had previously been found to use sulfur for chemosynthesis also, can use hydrogen. In some circumstances it may actual prefer hydrogen. Again, from R&D Magazine Online News:
The discovery began at the Logatchev hydrothermal vent field, at 3000 m depth on the Mid-Atlantic Ridge, an undersea mountain range halfway between the Caribbean and the Cape Verde Islands. The highest hydrogen concentrations ever measured at hydrothermal vents were recorded during a series of research expeditions to Logatchev.
According to Jillian Petersen, a researcher with Nicole Dubilier, “our calculations show that at this hydrothermal vent, hydrogen oxidation could deliver seven times more energy than methane oxidation, and up to 18 times more energy than sulfide oxidation”.